Treatment of collected sewage has become increasingly important in recent years. Generally, the public and various regulatory authorities increasingly believe that the environment is less able than was previously thought to naturally filter and purify itself from the myriad of pollutants dicharged from manufacturing facilities, cities, and other installations. One area of particular concern is disposal of sewage from pleasure craft operating on various lakes, rivers, and ocean water ways.
Owners and operators of boats and marinas are coming under increasing governmental regulation, particularly in the control of how boating activities impact the environment. Indiscriminate discharge of sewage into water ways is becoming more restricted. United States Coast Guard regulations govern discharges from boats. In many circumstances, these regulations restrict operators of pleasure craft from discharging effluents except into approved sanitary systems. Marine toilets on houseboats and other pleasure craft thus include holding tanks to receive sewage. The boat holding tanks may be purged at marinas or other facilities equipped with sanitary systems to receive and treat such waste. Such treatment systems however may have insufficient capacity for the increased demand arising from regulations which restrict dumping.
Typical marine toilets with holding tanks include a liquid chemical to provide initial disinfecting treatment of the waste, to reduce noxious odors and to maintain the sanitation of the marine toilet. Chemical treatment of waste in the holding tank is a temporary solution. The waste must still be transferred to an approved treatment facility.
Incineration of sewage provides an alternative to holding the waste materials for entry to a standard sewage treatment system. U.S. Pat. No. 2,882,534 describes an incinerator toilet having a sealable receptacle assembly which functions as a commode and treatment apparatus. A flame is dischargd from an ignition unit and a stream of high velocity air carries the flame inward and downward through a mixing tube into the incineration chamber. The flame is in direct contact with the waste. An agitator is rotated to break up solids in the waste and agitator rods expose particles of sewage to the hot flame. The liquids are vaporized and the solids are burned. Gases are discharged through a stack to the atmosphere. A latch member and a lock restrict the toilet from use while wastes are being combusted. After combustion and agitation stops, a blower continues to move air through the receptacle assembly for cooling. A thermal switch releases the lock when the temperature drops to a predetermined point permitting the toilet to be used again.
U.S. Pat. No. 3,765,035 describes a disposal system which dries and sterilizes sewage. Sewage collected from various receptacles is transferred through a conduit to a rotatable sphere. A gas heater is mounted within the sphere and includes a deflector plate or cone. The sphere rotates with a driving gear and it is heated to dry and sterilize the sewage. Muller balls of varying diameters roll about the bottom of the sphere to mash and squeeze the solid waste material. A vacuum pump removes vapors from the sphere. Residual solids are periodically removed from the sphere. Reversing the vacuum pump provides air pressure to expel the powders or solids into a tank, drum or other storage device.
Each of these described apparatus have drawbacks and disadvantages which limit their practicality for use on pleasure craft. Because space on pleasure craft and houseboats is at a premium, the marine toilet is typically placed in a small area. A complicated and bulky marine toilet with an integrated incinerator occupies space more valuable for other purposes. Also, a toilet facility on a boat which includes an integral incinerator would require special construction to receive and house the incinerator/toilet. Such construction includes triple wall framing to provide an interface between the incinerator and the area of the pleasure craft in which the apparatus is installed. Operation of the incinerator requires time for pre-heating and cooling. It is more economical to incinerate sewage which first accumulates in a holding tank. A holding tank also permits the marine toilet to remain available for use. Rather than using a spherical holding tank as a drying chamber, measured transfer of sewage into the incinerator provides more efficient and thorough combustion of the sewage.
The apparatus which uses a vacuum pump to remove vapors increases the complexity of the incinerator. Further, such a drying-type incinerator does not completely combust the waste particles and requires routine removal and disposal of residual solids. Accordingly, there is a need in the art to provide a environmentally acceptable compact sewage treatment apparatus for marine toilets.